I believe there are two types of creators of art - those who are naturally gifted, then those who have to work hard just to get to their level.
I personally am not naturally gifted. Like you I've practiced art for years, with little to no improvement in quality to the point that I thought "It'll be impossible to draw like so-and-so, even if I tried."
First of all, that is a misconception. Sure, not everyone has a natural knack at art and design. But that doesn't mean everyone can't learn how to draw something, and that doesn't mean the naturally gifted creators have the guts or determination to keep going.
Back then, I thought that my art would never be enough growing up, especially since both my twin sister and my dad had that natural talent. So anything that I thought I could try out and work on, I would be instantaneously one-upped by the closest people I knew, which was disconcerting to the point that I lost hope in creating in that field completely.
But for some reason... I went back to drawing and kept trying.
I kept practicing until all of those who were better than me stopped drawing to move on to other things. I kept practicing until I felt good about my art. I looked into anatomy, perspective, kept practicing, read a lot of manga, and kept practicing. Eventually I got a drawing tablet and thought again "Maybe I can draw digitally. It must be easier since there's layers to work with." Nope, I was very wrong. So I kept practicing.
After many years of trial and error, and I mean a lot of error, I got better.
I went from this:
(I drew this I think in 2008... )
to this:
And yet, I have little to no natural talent of my own. Instead, I've developed my skills through tiring practice, nurtured those skills, and now it's given birth to something that I can say "Wow. I used to draw like crap back then." Because I really did.
I still do. But it's better than before.
So, don't fret that people are against you. That's just how the world works. When someone sees something that they could never accomplish, they well push the person who made it down so they feel better about not being able to do the same. Working through adversity is one the best motivations for improvement, so do your best, keep practicing, and push forward. There's nowhere to go but up.